1. Field of the Invention
This invention relates to an image forming apparatus such as a photocopier, a printer, and the like capable of forming images on sheet materials by an image forming means made of an electrophotographic method, an ink jet method, or the like.
2. Description of Related Art
Color image forming apparatuses capable of high speed output of several tens of sheets per minute start to use practically these days. In such an apparatus, a method for forming full color images by transferring in an overlapping manner, e.g., four color toners of yellow, magenta, cyan, and black onto a sheet material according to the image information and by melting and mixing the toners by means of a fixing section has been used to form full color images. To mix the toners of four colors completely, the apparatus has a structure to apply heats in a large amount in a short time during fixing.
The sheet material thus formed with images is delivered onto a delivery tray located outside the apparatus by a delivery roller pair and is stacked on the tray.
However, the image forming apparatus of such a conventional technology embraces the following problems.
Because the sheet materials delivered on the delivery tray from the delivery roller pair right after the fixing process are ordinarily at a very high temperature, a large number of sheet materials heated at the high temperature is stacked on the delivery tray, so that toner images on the sheet materials may adhere to other sheet materials, or in some case, the sheet materials may adhere to each other, thereby rendering the image quality impaired.
In the apparatus of this type, a manual feed portion is provided for corresponding to various sheet materials (particularly, sheet materials having different thicknesses), and a sheet material conveyance route from the manual feed portion is frequently designed as to extend straightly. However, it was difficult to stack sheet materials orderly on the delivery tray in all cases, because a setting for stacking all of the sheet materials orderly on the delivery tray (e.g., conveyance speed or throwing angle of the delivery roller pair, angle of the delivery tray) is not easily, and because the sheet materials have different rigidity during delivery depending on image density, environments outside the apparatuses, kinds of the sheet materials, and the like.
To raise stacking easiness of the sheet materials having a smaller rigidity, many apparatuses have a structure that the delivery roller pair bends the sheet materials in the conveyance direction as the center of the sheet materials is curved downward, thereby delivering the sheet materials with certain rigidity.
However, where plastic sheet materials in a film form, like OHP sheets, are used, such sheet materials require a larger heat amount in comparison with the plain paper when toners are fixed, so that it is general to structure that a larger heat amount is given by rendering the sheet material conveyance speed slower at the fixing section. In such a situation, the toners after fixing tend to be cooled down slowly, and the sheet materials may be softened due to heats at the fixing section. Therefore, some trace of the delivery roller pair may be left on the sheet materials, or bending for giving rigidity may remain on the sheet materials and the sheet materials keep the shape without bending back even after sheet materials are cooled down.
It is therefore an object of the invention to provide an apparatus for preventing the image quality formed on the sheet materials from becoming inferior and for raising orderly stacking easiness of the sheet materials.
A representative structure of the invention to accomplish the above object is to include image forming means for forming images on sheet materials; delivering means for delivering the sheet materials on which images are formed; a delivery tray for receiving the delivered sheet materials; and fanning means capable of changing a blowing amount for fanning the sheet materials delivered from the delivering means to the delivery tray.
According to the above structure, the blowing amount for fanning the sheet materials delivered from the delivering means to the delivery tray can be changed, so that the image quality formed on the sheet material can be prevented from being impaired, and so that orderly stacking easiness of the sheet materials can be raised.
That is, when the sheet materials warmed by a fixing means are delivered onto the delivery tray, the air blow from the fanning means ensures fixation of the toner images upon cooling the sheet materials, so that the toner images can be maintained orderly even where the recorded sheet materials are stacked sheet by sheet on the delivery tray
To prevent warmed sheets when delivered onto the delivery tray from being folded due to a difference in level between the delivering means and the delivery tray in association with the kinds of the sheet materials, delivering means of a conventional apparatus was required to deliver the sheet materials as bent. However, in this invention, the air blow from fanning means supports the sheet materials from the lower side of the materials, so that the sheet materials need not to be bent likewise the conventional apparatus, so that the apparatus can prevent the sheet materials from deforming.
Moreover, according to the conditions such as e.g., kinds of the sheet materials, the air blowing amount of the fanning means can be changed, so that the sheet materials can be stacked orderly.